Sampling of Trace Volatile Metal(loid) Compounds in Ambient Air Using Polymer Bags: A Convenient Method

摘要

The sampling of volatile metal(loid) compounds (VOMs) such as hydrides, methylated, and permethylated species of arsenic, antimony, and tin is described using Tedlar bags. Advantages as well as limitations and constraints are discussed and compared to other widely used srm-pling techniques within this area, namely, stainless steel canisters, cryotrapping, and solid adsorbent cartridges. To prove the suitability of Tedlar bags for the sampling of volatile metal(loid) compounds, series of stability tests have been run using both laboratory synthetic and real samples analyzed periodically after increasing periods of storage. The samples have been stored in the dark at 20 “C and at 50 “C. Various volatile arsenic species (AsH3, MeAsH2, Me2AsH, MeaAs), tin species (Sulk, MeSnH3, Me2SnH2, Me3SnH, Me4Sn, BuSnH3), and antimony spe-cies (SbH3, MeSbH2, Me2SbH, Me3Sb) have been gener-ated ~using hydride generation methodology and mixed with moisturized air. Three static gaseous atmospheres with concentrations of 0.3—18 ng/L for the various compounds have been generated in Tedlar bags, and the stability of the VOMs has been monitored over a period of 5 weeks. Sewage sludge digester gas samples have been stored only at 20 “C for a period of 48 h. Cryotrapping GC/ICPMS has been used for the determination of the VOMs with a relative standard deviation of 5% for 100 pg. After 8 h, the recovery rate of all the compounds in the air atmospheres was better than 95% at 20 and 50 “C, whereas the recovery after 24 h was found to be between 81 and 99% for all VOMs at 20 and 50 “C except for Me3Sb and Me3As. These species show a loss between 48 and 73% at both temperatures. After 5 weeks at 20 “C, a loss of only 25—50% for arsine and stibine and the above-mentioned tin compounds was determined. Only MeaSb, Me3Bi, and Me2Te were present in the digester gas sample. After 24 h, losses of 44, 10, aAd 12%, respectively, could be determined. Given these results, Tedlar bags could even be used, with some limitations, for long-term sampling of air containing traces of VOMs. The loss is more pronounced at higher temperatures.